The tendency of a force to rotate an object about an arbitrary axis.

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40 views

Torque as if magnetic force were concentred in mean point

From what I see in my textbook and several on line resources (such as this, p. 8-8), I am tempted to think that the magnetic force $I\boldsymbol{\ell}\times\mathbf{B}$ acting on a straight conducting ...
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1answer
63 views

Rotational equilibrium Paradox

A block of mass M and height h is moving on a rough surface of coifficent of friction 0.5 .The block is moving with a velocity v at some instant. if we balance the torque due to frictional force and ...
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1answer
23 views

Changing angular momentum with no forces to do torque

Suppose a particle of mass $m$ moves in a straight line at velocity $v$ some distance away from an axis, as shown here at times t1 and t2 (where the axis of rotation is located at the origin of the ...
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1answer
65 views

Torque and Angular Momentum

An ice skater is spinning in a circle with an angular velocity, $\omega$, and rotational inertia $I$. Let's say that the skater then pulls his arms directly inwards at a constant rate over a time of $...
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50 views

What kind of torques cause an object to precess?

In studying precession, my textbook (Taylor's Classical Mechanics) makes the assumption that a top spinning about its symmetric axis, but tipped at an angle $\theta$, will precess nicely so long as ...
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1answer
50 views

Angular acceleration of a car door [closed]

http://imgur.com/F3eAF9F Edit: i uploaded to the site but it came out really blurry so heres the imgur link I don't get the solution at all, where does the -ma r cos theta come from? (Sorry on my ...
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2answers
111 views

Couldn't high gear ratio replace need for high torque engines?

I've noticed that there is a correlation between displacement and torque, so trucks, SUVs etc. have large displacement engines to produce lots of torque to move heavy loads. Sports cars have lower ...
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0answers
66 views

How to calculate motor torque & rpm

I watched a DIY video recently about a brushless DC motor. How would one go about calculating the max torque & max rpm (under no-load & a given load conditions) of that motor based on the ...
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0answers
24 views

How can I calculate the torque of draw force which affect on spinning ball flying in the air?

I am studying the Magnus effect on a flying ball i have calculate the magnus force but i trying calculate the angular acceleration, because the angular velocity of the ball is not constant. I have ...
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0answers
26 views

What point is the torque on a loop in a magnetic field taken about?

I know that the torque on a loop kept in uniform magnetic field is given by $$\vec{\tau}=\vec{M}\times\vec{B}$$ where $\vec{M}$ is magnetic moment. Now, can I take this torque about any point in ...
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1answer
71 views

What is a moment/torque?

What is a moment/torque? i know the formulas m = fxd (Nm), I know how it works, what is does etc. But think of it fundamentally, how is it possible, that a force becomes greater when the arm of an ...
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1answer
305 views

Angular momentum paradox with 2 identical gears

Consider two identical gears touching each other. The system is friction less. One has a handle that you use to apply a torque on the entire system. If you turn the handle, there will be a non-zero ...
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2answers
60 views

Torsion and twist in solid cylindrical beam

Well given a beam (as shown), a solid cylinder with radius R. A Torque $T$ applied to it, I need to solve the angle of twist ($\theta$) at the position where the torque is applied ($z$). The basic ...
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0answers
27 views

What is the general proof that the torque acting on an irregular current carrying loop in an uniform magnetic field is only dependent on area?

How do you prove that the torque acting on an irregular current carrying loop in an uniform magnetic field in the plane of loop = $I \vec{A} \times \vec{B}$ Where, $ \vec{A}$ = Area vector of the ...
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0answers
20 views

Total torque from direction cosines

I'm trying to determine an expression for the total torque on a rigid cylindrically-symmetric body subject to a rotational potential $\phi$. Let the orientation of the body be given by a unit vector e,...
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2answers
56 views

Is it okay to use the same moment of inertia formula for both a door turning on hinge and a long thin rod rotating at its end?

My book says you can redistribute the mass elements of a object to simplify its moment of inertia formula. But squeezing a door into a rod would change its density. Does it matter?
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1answer
31 views

Why does a ball rotate sometimes when you throw it?

My guess is that when you throw a ball, which is held by your hand, using you arm, the radius of the circular path being constant, the outermost part of the ball has a bigger radius than the innermost ...
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1answer
32 views

What are some characteristics of r as in $\tau = mr^2\alpha$?

Can r just be the distance from an object center of mass to the axis of rotation? If not, it will be very hard to calculate r for things that are not particles, which doesn't exist in real life. ...
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0answers
28 views

what is significance of direction of vector product(torque & angular momentum)?how can one use them practically? [duplicate]

since i came across vector product or cross product i have one doubt that is what direction of torque shows.the direction of product is along axis of rotation(+ve or -ve).is there is any practical use ...
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2answers
1k views

How bicycle gear works?

Based on the concept of the moment of inertia, my book gives the following relationship between the size of gear and amount of torque supplied to the drive wheel: Because it [outermost gear] had ...
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3answers
107 views

What is the difference when we measure torque/angular momentum about a point and about an axis?

When do we measure torque about an axis and when do we measure torque about a point?Whats the difference? I tried searching this on google but did not get satisfactory answer.
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1answer
48 views

Finding the coefficient of friciton [closed]

I'm asked to find the coefficient of friction before the bar starts sliding. Here is my solution -> ∑M = 0 -mg * 1.4863 + 1.8159*T = 0 (T*1.8159) i found by using a cross product ( -2.9726i+ 2....
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1answer
105 views

Who told us how to measure torque?

We all know that force and torque are physical quantities which we have defined according to our purpose of work. Now we are all aware that Newton's Second Law from his Laws of Motion states how to ...
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0answers
33 views

How rotational force calculation depends on the distance between the point of force application and the axis of rotation?

I don't understand how the perpendicular distance between the point of force and the axis of rotation gets involved in the calculation of the rotational effect of that force.Is it about rotational ...
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1answer
30 views

Finding the friction before slipping [closed]

There is a string that is attached to a bar as shown below in the picture. What is the coefficient friction between the bar and floor before bar starts slipping. I have chosen a pivot point about ...
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2answers
82 views

Equilibrium equations

You have one horizontal beam. Its left point is attached to a free pivot at the vertical wall. Its right point is suspended by a rope from the ceiling. Nothing is moved. So $\sum F=0$ and $\sum M=0$. ...
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1answer
46 views

A leaf floating on the surface of water (in $x$-$y$ plane) curl along positive $z$ axis [closed]

A leaf floating on the surface of water (in x-y plane) show that for a very small circular leaf ($\nabla \times \overrightarrow v $) is equal to twice the angular velocity of rotation of the leaf, ...
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0answers
15 views

How do I calculate the best mass for the highest linear speed?

I have a motor whose specifications say that its torque is 190g*cm. If I have the formula for the mass of the wheel vs radius, is there any way I can find the optimal radius to get the highest linear ...
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3answers
316 views

Does KV in rc motors (RPM/Volt) tell us anything about the torque?

Considering that KV is RPM/Volt, does it ever tell us anything about the torque? Wouldn't you need to be told the torque separate from the KV rating? If torque can be derived from a KV rating then ...
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0answers
102 views

Moment of Inertia of a Motion Simulator Frame

I have a rather specific question. I'm trying to build a motion simulator for flight and racing sims, similar to this: https://www.youtube.com/watch?v=JQAZB3EnI_w . The basic concept is a platform ...
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1answer
275 views

torque in electric dipole placed in nonuniform electric field

In the uniform electric field case, we can know the rotational axis is at the position in the middle of positive charge and negative charge. However, if the electric field is non-uniform, or simply ...
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1answer
44 views

Acceleration of two points problem (mathematical explanation)

There is a square board with two nails in corner A and B. We apply a torque $M$ to the square board. Nail A can move freely on a track only in the $x$ direction and B only in the $y$ direction. The ...
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35 views

Why does a balance try to be horizontal? The moments are equal [duplicate]

Suppose we have an ordinary balance where equal weights are put in both sides. Now one side is slowly held down. When this force is not applied anymore, the balance tends to achieve horizontal ...
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3answers
39 views

Minimizing time of a rotating pole

I've been trying to solve this problem for a while now but I'm not sure exactly what I must do in this scenerio. The scenerio is as follows: There is a pole of arbitrary length attached to a point ...
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1answer
411 views

Finding torque due to normal force [closed]

A cubical block of mass $m$ and edge length $a$ slides down a rough inclined plane of inclination $\alpha$ radian with a uniform speed. Find the torque of the normal force acting on the block about ...
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1answer
227 views

Why is torque the cross product of the radius and force vectors?

I understand the torque vector to be the cross product of the radius (moment arm) and force vectors, but that means the torque would be perpendicular to the radius and force vectors, which makes no ...
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1answer
115 views

Doubt related to rotational motion (rolling down an inclined plane)

I have doubt regarding when an object ( sphere , ring , cylinder etc ) rolls down a FRICTIONLESS inclined plane. Let us suppose the angle of inclination of inclined plane is θ. Now the forces acting ...
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1answer
188 views

Confusion between TWO shear stress formulas

There are two formulas that I have encountered so far for shear stress in my Engineering class. Let S be shear stress, F be force, and A be cross sectional area: S = F/A Note: This formula is ...
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1answer
117 views

Torque when net external force is zero

I was studying force couple and my teacher said that in this the torque about any point is same. That led me to wonder if in any case if net external force is zero then is torque about any point in ...
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1answer
96 views

Contradiction in a simple torque/rotation problem - two ways of calculating external force don't agree

Suppose we have a rigid system of two point objects (both of unit mass) connected with a massless rod, with the objects horizontal on the x axis, at a distance $r_1$ and $r_2$ from the origin, ...
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1answer
75 views

Lever Mechanical Advantage

In the attached image the force output of the plank is calculated to be the work done (FDf) divided by the height the block rises (Dw). So the force the plank applies on the block is (FDf)/(Dw). But ...
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2answers
219 views

How to calculate force / torque on non-flat lever, i.e. dolly

See attached image. The mass is being rotated on a lever where the pivot point (P) is a certain distance ($L_2$) from the right angle at the bottom. How do I calculate the force necessary to apply ...
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2answers
190 views

Apply force to one end of a rod in space: why not purely translational? [duplicate]

Why does applying force to a rod in space (or any other isolated systems) on one end leads to both translational and rotational motion? Here's my logic: suppose there is a rod in space. We ...
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1answer
37 views

Why can't we have more than 3 moment equations in equilibrium equations

Excuse me for a kind of stupid question but, In statics of a 3D rigid body, the equations to determine equilibrium are at most 6 (Fx Fy Fz Mx My Mz = 0) (not counting those from hinges and rollers). ...
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1answer
165 views

Question about Torque Reaction of a Helicopter

This image below about the torque reaction of a helicopter has confused me a bit. I would like to ask whether i understand the principles here correctly. In the picture we see a helicopter whose main ...
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2answers
185 views

More torque or more horsepower? Which engine is more powerful [closed]

Two internal combustion engines : $250\,\mathrm{hp}$ and $900\,\mathrm{Nm}$ torque $770\,\mathrm{hp}$ and $790\,\mathrm{Nm}$ torque Which of the above two engines will be more powerful? P.S. ...
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1answer
63 views

Rotational motion - torque

I recently read a book of introduction of the rotational motion, but I do not quite understand the way author analysed the problem. Situation: A light rod rests on a pivot passing throughout its ...
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0answers
24 views

How is the torque on the support?

I simulated with Spaceclaim Ansys this device I would like to study: https://youtu.be/Pjc4dIf1aWI The friction is very low. I drawn a fixed black circle on the orange disk to look at the angular ...
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1answer
55 views

Will a coin topple if the center of the coin is just on the corner of the square table?

3/4th of the coin is outside the table and 1/4th is on the inside. Also assume that the center of the coin is just on the inside.
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1answer
203 views

Calculating output forces of bicycle wheels

Based on the force on the rear gear $F_t$ and the radii of the rear gear $R_g$ and rear wheel $R_w$ , how would you calculate the force the bicycle exerts on the ground when it is accelerating? I ...